Health and Human Texas Department of State Services Health Services Arbovirus Activity in Texas 2018 Surveillance Report August 2019 Texas Department of State Health Services Zoonosis Control Branch Overview Viruses transmitted by mosquitoes are referred to as arthropod-borne viruses or arboviruses. Arboviruses reported in Texas may include California (CAL) serogroup viruses, chikungunya virus (CHIKV), dengue virus (DENV), eastern equine encephalitis virus (EEEV), Saint Louis encephalitis virus (SLEV), western equine encephalitis virus (WEEV), West Nile virus (WNV), and Zika virus (ZIKV), many of which are endemic or enzootic in the state. In 2018, reported human arboviral disease cases were attributed to WNV (82%), DENV (11%), CHIKV (4%), ZIKV (2%), and CAL (1%) (Table 1). In addition, there were two cases reported as arbovirus disease cases which could not be diagnostically or epidemiologically differentiated between DENV and ZIKV. Animal infections or disease caused by WNV and SLEV were also reported during 2018. Local transmission of DENV, SLEV, and WNV was documented during 2018 (Figure 1). No reports of EEEV or WEEV were received during 2018. Table 1. Year-End Arbovirus Activity Summary, Texas, 2018 Positive Human* Arbovirus Mosquito Avian Equine TOTAL TOTAL Fever Neuroinvasive Severe Deaths PVD‡ Pools (Human) CAL 1 1 1 CHIK 7 7 7 DEN 20 20 20 SLE 2 0 2 WN 1,021 6 19 38 108 146 11 24 1,192 Zika** 4 4 TOTAL 1,023 6 19 65 109 0 178 11 24 1,226 CAL - California serogroup includes California encephalitis, Jamestown Canyon, Keystone, La Crosse, Snowshoe hare and Trivittatus viruses CHIK - Chikungunya DEN - Dengue SLE - Saint Louis encephalitis WN - West Nile ‡PVD - Presumptive viremic blood donors are people who had no symptoms at the time of donating blood through a blood collection agency, but whose blood tested positive when screened for the presence of West Nile virus or Zika virus. Unless they meet the case reporting criteria, they are not counted as a case for official reporting purposes and are not included in the "Total" columns. *Does not include two cases which could not be differentiated between dengue and Zika viruses. **Zika disease cases California Serogroup Viruses California serogroup viruses are bunyaviruses and include California encephalitis virus (CEV), Jamestown Canyon virus, Keystone virus, La Crosse virus (LACV), snowshoe hare virus, and Trivittatus virus. These viruses are maintained in a cycle between mosquito vectors and vertebrate hosts in forest habitats. In the United States (U.S.), approximately 40-100 reported cases of human neuroinvasive disease are caused by LACV each year, mostly in mid-Atlantic and southeastern states. From 2002-2017, Texas reported a total of five cases of human CAL serogroup virus disease (range: 0-3 cases/year): one case of CEV neuroinvasive disease and four cases of LACV neuroinvasive disease. In 2018, Texas reported one travel-associated human case of LACV neuroinvasive disease. Arbovirus Activity in Texas ‐ 2018 Surveillance Report, DSHS Page 2 of 14 Figure 1. Texas Counties Reporting Arbovirus Activity* in Any Species, 2018 Tera, Defartmeot of State H•akh and inma n Services H.. lth s«Yla,, ~ Coun ty w ith Dengue Virus Activity I I I I [ I I I I I I I I I I I I ~ Coun ty w ith St Louis Encephalitis Virus Activity 0 25 50 100 150 200 250 Mil es - Coun ty w ith West Nile Virus Acti vity * Indicated by an arbovirus-positive bird, mosquito pool, sentinel chicken, horse, or human (disease case or presumptive viremic donor). Excludes imported cases of chikungunya, dengue, Zika, and other arboviruses. Absence of reported activity from counties may be due to absence of a surveillance program for non-human cases. Arbovirus Activity in Texas ‐ 2018 Surveillance Report, DSHS Page 3 of 14 Chikungunya Virus Chikungunya virus is an alphavirus that is maintained in a cycle between Aedes aegypti or Ae. albopictus mosquitoes and human hosts. Since 2004, several extensive outbreaks have been reported from countries in Africa, Asia, Europe, and the Indian and Pacific Oceans. In late 2013, the first local transmission of CHIKV in the Americas was reported in the Caribbean. Since then, locally-acquired cases of chikungunya disease (CHIK) have been reported throughout the region, including the U.S. Prior to the emergence of CHIKV in the Americas in 2013, Texas had reported fewer than five travel-associated CHIK cases. In contrast, from 2014- 2017, Texas reported a total of 203 travel-associated CHIK cases (range: 15-114 cases/year) and one locally-acquired case in Cameron County (2015) (Figure 2). In 2018, Texas reported six travel-associated cases of CHIK, one case where travel status was unknown as the case was lost to follow-up, and no locally-acquired cases. Reported cases traveled to India (50%), Aruba (17%), Mexico (17%), and the Philippines (17%). Figure 2. Human Chikungunya Cases Reported in Texas, 2014-2018 120 ell QJ 100 ell n, u "C QJ 80 ~ 0 c.. QJ 60 .....0::: 0 i.. QJ 40 .c E ~ 2 20 0 2014 2015* 2016 2017 2018 Report Year Incl udes one locally-acquired case Dengue Virus Dengue virus is a flavivirus that is maintained in a cycle between Ae. aegypti or Ae. albopictus mosquitoes and human hosts. It is established throughout the tropical and subtropical Americas, including northern Mexico. Human cases are most often imported into the U.S. as a result of travel to a dengue-endemic country, but locally-acquired cases have been reported in Florida, Hawaii, and Texas. From 2003-2017, Texas reported a total of 403 cases of dengue (annual median = 21 cases, range: 1-95 cases/year). During this time period, 27 cases of locally- Arbovirus Activity in Texas ‐ 2018 Surveillance Report, DSHS Page 4 of 14 acquired dengue were reported from the Lower Rio Grande Valley region of Texas: 24 in Cameron County, 2 in Hidalgo County, and 1 in Willacy County. In 2018, Texas reported 19 travel-associated cases of dengue and one locally-acquired case of dengue in Starr County (Figure 1). This local transmission event likely resulted from increased dengue transmission in the neighboring Mexican states of Tamaulipas and Nuevo Leon during the fall of 2018. The majority of cases reported travel to Mexico (25%), India (25%), and Southeast Asia (20%) (Figure 3). Figure 3. Reported Cases of Dengue by Country of Acquisition, Texas, 2018 (N = 20) Not Imported Vietnam 5% 5% Sri Lanka 5% India 25% Philippines 5% Guatemala 5% Bangladesh 5% Thailand Mexico 10% 25% Cuba 10% Saint Louis Encephalitis Virus Saint Louis encephalitis (SLE) virus is a flavivirus maintained in a cycle between Culex species mosquitoes and birds, with occasional transmission to humans. The geographic range of SLEV extends from North to South America, but the majority of human cases have occurred in the eastern and central U.S., where periodic epidemics have occurred since the 1930s. In Texas and states with milder climates, SLEV can circulate year-round. From 2003-2017, Texas reported 38 cases of SLE in humans (annual median = 1 case, range: 0-18 cases/year). In 2018, two SLEV- positive mosquito pools were identified in El Paso County (Figure 1). No human cases of SLE were reported in 2018. Arbovirus Activity in Texas ‐ 2018 Surveillance Report, DSHS Page 5 of 14 West Nile Virus West Nile virus is a flavivirus maintained in a cycle between mosquitoes (primarily Culex species) and birds. West Nile virus circulates on every continent except Antarctica. Before 1999, WNV had not been documented in the Western Hemisphere. In 1999, human disease associated with WNV infection was identified in New York City. By the end of October 1999, WNV infections had been confirmed in multiple native species of birds as well as horses from New York City and areas within a 200-mile radius. Since 1999, WNV infections in humans, birds, equines, other animals, and mosquitoes have been reported throughout the U.S. West Nile virus was first reported in Texas in 2002. Initially, only West Nile neuroinvasive disease (WNND) was reportable in humans; West Nile fever (WNF) became a reportable condition in 2003. From 2002-2017, a total of 5,412 human WNV disease cases were reported in Texas (annual median = 198.5 cases, range: 27-1,868 cases/year). In 2011, Texas reported its lowest number of human WNV disease cases, 27, but then a record high number of 1,868 cases were reported in 2012 (Figure 4). In 2018, 146 human WNV disease cases were reported: 108 (74%) WNND and 38 (26%) WNF. Additionally, there were 24 presumptive viremic blood donors (PVDs) reported by blood collection agencies; these individuals are asymptomatic blood donors who test positive for WNV on donor screening tests and represent likely infections with WNV. Presumptive viremic donors are not considered cases unless symptoms consistent with WNV disease develop within two weeks of their positive blood screening test and follow-up testing verifies the infection. Figure 4. Human West Nile Disease Cases Reported in Texas, 2002-2018 2000 VI 41 1800 VI .,,uta 1600 41 1400 °S 1200 i 1000 ci:: 0... 800 41 600 .c E 400 ::::, z 200 0 Report Year ■ West.Nile Fever ■ West.Nile Neuroinvasive Disease West Nile Fever was not reportable in Texas in 2002 Arbovirus Activity in Texas ‐ 2018 Surveillance Report, DSHS Page 6 of 14 During 2018, evidence of WNV activity (human, horse, bird, mosquito, or sentinel chickens) was reported from 58 (23%) of the 254 counties in Texas (Figure 1). Twenty-four (9%) counties reported WNV-positive mosquito pools, 43 (17%) reported human WNV disease cases, 8 (3%) reported PVDs, 16 (6%) reported equine WNV disease cases, and 1 (~1%) county reported WNV-positive birds.